1. Field of the Invention
The present invention relates to a fitting for a circuit-interrupting device and to apparatus for mounting the fitting to the circuit-interrupting device. More specifically, the present invention relates to an end fitting for a high-voltage fuse unit and to apparatus for mounting the end fitting to the fuse unit.
2. Description of the Prior Art
Fuse units of various constructions are well known. Such fuse units include a fusible element, movable arcing rod (or arcing contact), a body of arc-extinguishing material and mechanisms, such as srings, for biasing the arcing rod toward movement. Normally, the fusible element and the arcing rod are connected between conductive end ferrules on the fuse unit to complete a circuit therebetween. Melting of the fusible element in response to an over-current condition permits the biasing mechanism to move the arcing rod through a bore in the arc-extihguishing material. The interaction between the high-voltage arc thereby struck and the arc-extinguishing material ultimately extinguishes the arc. Fuse units generally include an elongated, insulative, tubular body between the conductive end ferrules for housing the various parts thereof. The end ferrules are attachable to appropriate end fittings which are in turn selectively engageable with or disengageable from appropriate fuse mountings spaced insulatively apart on an appropriate structure. The fuse unit, with the end fittings mounted thereon, is referred to as a fuse.
The prior art recognizes at least two types of fuses, namely, outdoor and indoor. Outdoor fuses generally have end fittings mounted to their fuse units which may be associated with mountings that permit the fuse to dropout upon operation thereof. Specifically, such end fittings and mountings are designed to permit one of the end fittings to rotate in its associated mounting so that the fuse may rotate about the mounting upon operation of the fuse, thus giving a visual indication of fuse operation.
Outdoor fuse operation is generally accompanied by the exhausting or venting of gases from an end of the fuse. The gases may be partially conductive, but this is of little or no concern in outdoor environments since adjacent energized gear is adequately spaced.
Outdoor fuses often contain mechanisms at the exhaust end which prevent the entry of rain or other water into the fuse. Such rain or water may prevent proper operation of the fuse. These facilities may take the form of a rain cap selectively attachable to the exhaust end of the fuse which permits the gases to be vented therefrom upon fuse operation, but which prevent rain and water entry.
Fuses used indoors or in enclosures generally do not operate in a dropout mode. The end fittings and mountings of indoor fuses, however, permit them to be selectively disengaged and engaged at one end upon limited rotation of the other end for replacement of the fuse or other servicing. There is no need for a rain cap or the like in indoor environments since the fuses are usually contained within enclosures or other confined spaces. However, control of the exhaust from the fuse end becomes important in indoor environments where high gas pressures may deleteriously affect enclosures and where gases which may be conductive may adversely affect the insulators of, or the insulating space between, adjacent energized gear. Accordingly, indoor fuses usually have exhaust control facilities which control both the pressure of gases exhausted from the fuse and the contents of such gases.
Because outdoor and indoor fuses are used in different environments, and because the mountings and end fittings of these two fuse types are generally different, prior art fuse units have been divergent in construction and structure, depending on their intended environment of use, even though they have similar voltage and current ratings.
It would be an improvement over the prior art to provide a single universal fuse unit usable with varying end fittings which permit the same fuse unit to be placed in indoor or outdoor environments. Moreover, it would be an improvement over the prior art to provide an indoor fuse unit end fitting which is simple to construct and to assemble to the fuse unit. Such an end fitting should have a minimum of parts, should be easy to manufacture, and should conveniently adapt the universal fuse unit to indoor usage.